Small Incision Lenticule Extraction (SMILE) for Hyperopia: Optical Zone Diameter and Spherical Aberration Induction.

PURPOSE: To evaluate optical zone diameter efficacy and spherical aberration change in hyperopic small incision lenticule extraction (SMILE).

METHODS: Prospective study of 60 consecutive hyperopic SMILE procedures using the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) and matched LASIK procedures with the VisuMax and MEL 80 excimer (Carl Zeiss Meditec) lasers. Inclusion criteria were maximum attempted hyperopic meridian of between +1.00 and +7.00 diopters (D). For SMILE, the transition zone was 2 mm and the mean optical programmed zone was 6.37 mm (range: 6.3 to 6.7 mm). Two LASIK control groups (6.5- and 7-mm optical zone) matched for spherical equivalent treated were generated. Both tangential and axial curvature difference maps were generated for each eye at 3 months. A fixed grid and set of concentric circles were superimposed on the difference map to measure the achieved optical zone diameter.

RESULTS: Mean attempted spherical equivalent refraction was +5.58 ± 0.95 D (range: +3.20 to +6.50 D) in the SMILE group. By tangential mapping, SMILE programmed at a mean optical zone of 6.37 mm achieved a diameter of 5.03 ± 0.30 mm, similar to 7-mm LASIK (4.96 ± 0.25 mm, P = 0.33) but larger than 6.5-mm LASIK (4.53 ± 0.25 mm, P < .001). By axial mapping, the achieved optical zone diameter was 6.75 ± 0.31 mm for 6.37-mm SMILE, larger than for both 6.5-mm (6.61 ± 0.21 mm) and 7-mm (6.92 ± 0.14 mm) LASIK (P < .01). Spherical aberration changed on average by -0.45 ± 0.22 μm for 6.37-mm SMILE, similar to 7-mm LASIK (-0.50 ± 0.21 μm, P = .29) and less than for 6.5-mm LASIK (-0.69 ± 0.22 μm, P < .001).

CONCLUSIONS: The mean achieved optical zone diameter of hyperopic SMILE was found to be larger than the mean achieved optical zone diameter of hyperopic LASIK. Consequently, spherical aberration induction was similar for 6.37-mm SMILE and 7-mm LASIK. [J Refract Surg. 2017;33(6):370-376.].